Coaxial attenuation equalizer



April 28, 1963 s. J. szczuKA 3,087,126

COAXIAL ATTENUATION EQUALIZER Filed Jan. 25. 1961 IMVER ELECTRODE OF COAXIAL CPACITOR INVENTOR. STANLEY J Szczuka United States Patent O 3,087,126 COAXIAL ATTENUATION EQUALIZER Stanley J. Szczuka, Commack, N.Y., assignor to Sperry Rand Corporation, Great Neck, N.Y., a Corporation of Delaware Filed Jan. 25, 1961, Ser. No. 84,952 Claims. (Cl. 333-28) The present invention relates to attenuation equalizers and, more particularly, to an attenuation equalizer of the coaxial type adapted for operation at very high frequencies.

As is well understood in the art, an equalizer is an electrical circuit which is placed intermediate a signal generator and a load to control the current that the generator produces in the load in some predetermined manner as a function of the frequency of the signal. An attenuation equalizer is an equalizer which controls the magnitude of the load current as a function of signal frequency.

One of the most widely employed types of attenuation equalizer networks is of a bridged T configuration having an attenuation or insertion loss characteristic which increases in db substantially linearly With the frequency of the applied signal. It can be shown, however, that a linearly increasing insertion loss characteristic cannot be achieved when the frequency of the applied signal increases. within the VHF band which extends from 30 megacyeles per second to 300 megacycles per second unless special design techniques are employed. In the case where conventional lumped Constant circuit elements are inter-connected in bridged T configuration, the atttenuation versus frequency characteristic begins to depart from the desired linear relationship as the frequency of the applied signal increases through the upper portion of the VHF band., The change in the attenuation characteristic of such higher frequencies is attributable to frequency induced changes in the magnitude of the impedances presented by the lumped elements employed in the equalizing network.

It is the general object of the present invention to provide an attenuation equalizer having -a db insertion loss versus frequency characteristic which remains linear throughout the VHF band.

` Another object is to provide a simple and easily reproduced attenuation equalizer adapted for operation in the range of frequencies from 30 megacycles per secone to 300 megacycles per second. A further object is to provide an attenuation equalizer wherein the constituent circuit elements are compactly mounted in a housing which acts as an electrical shield.

These and other objects of the invention, as will appear from a reading of the following specification, are achieved in a preferred embodiment by the provision of an inner and an outer hollow cylinder of conductive material mounted in coaxial relationship. The opposing surfaces of the inner and outer cylinders are separated by a dielectric sleeve. An inductive element and a pair of discs of resistive material are also provided. Each end of the inductive element is connected to a respective one ofi said resistive discs. The resistive discs, in turn, which have a radius of curvature conforming to that of the inner conductive cylinder, support the inductive element axially within said inner cylinder.

The input and output of the equalizer are adapted for connection in a conventional coaxial line. The center conductor of the input coaxial line is directly connected to one of the resistive discs; the center conductor of the output coaxial line is directly connected to the other of the resistive discs. The outer conductors of both the input and output coaxial lines are directly connected to the outer cylinder of the attenuation equalizer.

ICC

For a more complete understanding of the present invention, reference should be had to the following specification and to the drawings of which:

FIG. 1 is a schematic representation of a conventional attenuation equalizer of the bridged T type having an insertion loss versus frequency characteristic resembling that of the present invention;

FIG. 2 is a cross-sectional view of -a preferred embodiment of the present invention; and

FIG. 3 is a sectional view of the embodiment of FIG. 2 taken along the line 3-3.

The conventional equalizer network of FIG. 1 is described in Terman, Radio Engineer's Handbook, Mc- Graw-Hill Book Company, Inc., 1943, on pages 244-248. As is well understood, the circuit of FIG. 1 will produce'a substantially linear db insertion loss versus frequency characteristic so long as the values of the circuit constants remain unchanged throughout the range of the applied input signals. When the input signal frequency increases to a point where the nominally capacitive element, for example, exhibits an appreciable inductive characteristic, an undesired departure from the linear insertion loss vs. frequency relationship begins to appear. It has been found, however, that the desired relationship can be extended into the upper VHIE` band by modification of the structural elements comprising the equalizer network in accordance with the present invention.

Referring to the preferred embodiment of FIGS. 2 and 3, each end of the inductive element 1 is connected to and supported by a respective one of resistive discs 2 and 3. Discs 2 and 3, in turn, are mounted within inner hollow conductive cylinder 4 whereby continuous electrical contact is made between the circumference of discs 2 and 3 and the inner surface of cylinder 4. Cylinder 4 is coaxially positioned within outer hollow conductive cylinder 5 by means of -a dielectric sleeve 6. Cylinders 4 and 5 and dielectric sleeve 6 correspond to capacitor 7 of FIG. 1. Discs 2 and 3 correspond, respectively, to resistors 8 and 9 while inductive element 1 corresponds to inductor 10.

I External circuit connections are made via conventional coaxial connectors 13 and 14. lrnpedance matching devices 15 and ;16 couple the input and output of the attenuation equalizer, respectively, to the coaxial connectors 13 and 14. Input line 17 of inductive element 1 is directly connected to the center conductor of coaxial connector 13. The outer conductor of connector 13 is el'ectrically connected to outer cylinder 5. Output line 18 of inductive element 1 is directly connected to the center conductor of output connector 14. The outer conductor of connector 14 is electrically connected to outer cylinder 5.

lit will be seen that cylinders 4 and '5 not only constitute the opposing conductive plates of the capacitive com- `ponent of the attenuation equalizer but also act as an electrical Shield enclosing said equalizer thereby preventing undesired coupling to external eircuits. In addition, the lead wires for interconnecting the components in the conventional arrangement of FIG. 1 have been eliminated. This further stabilizes the values of the circuit constants against Variation with' frequency particularly at high frequencies.

While the invention has been described in its preferred embodiments, it is understood that the words which have been used are Words of description rather than of limitation and that changes within the purview of the appended claims may be made without departing from the true scope and spirit of the invention in its broader aspects.

What is claimed is:

1. An attenuation equalizer of the coaxial type having a pair of input terminals and a pair of output terminals and adapted for operation at very high frequencies, said equalizer comprising an inner and an outer hollow cylinder of conductive material mounted in coaxial relationship, the outer surface of said inner cylinder being separated from Vthe inner surface of said outer cylinder by a dielectric medium, an inductive element having an input and an output terminal, first and second resistive means, said first resistive means supporting one end of said inductive element within said inner cylinder and interconnecting said input terminal of said inductive element and the inner surface of said inner cylinder, and said second resistive means supporting the other end of said inductive element within said inner cylinder and interconnecting said output terminal of said inductive element and the inner surface of said inner cylinder, said outer cylinder and said input terminal of said inductive element comprising said pair of input terminals, and said outer cylinder and said output terminal of said inductive element comprising said pair of output terminals.

2. An attenuation equalizer having a pair of input terminals and a pair of output terminals and adapted for operation at very high frequencies, said equalizer comprising an inner and an outer hollow cylinder of conductive material, a hollow cylindrical sleeve of dielectric material for supporting said inner cylinder coaxially within said outer cylinder, said sleeve separating the inner surface of said outer cylinder from the outer surface of said inner cylinder, an inductive element having an input and an output terminal, first and second resistive means, said first resistive means supporting one end of said inductive element within said inner cylinder and interconnec'ting said input terminal of said inductive elementand the inner surface of said inner cylinder, and said second resistive means supporting the other end of said inductive element within said inner cylinder and interconnecting said output .terminal of said inductive element and the inner surfaces of said inner cylinder, said outer cylinder and said input terminal of said inductive element comprising said pair of input terminals, and said outer cylinder and said output terminal of said inductive element comprising said pair of output terminals.

3. An attenuaition equalizer adapted for operation at very high frequencies, said equalizer comprising an inner and an outer hollow cylinder of conductive material, a hollow cylindrical sleeve of dielectric material for supporting said inner cylinder coaxially within said outer cylinder, said sleeve separating the inner surface of said outer cylinder from the outer surface of said inner cylinder, an inductive element having an input terminal and an output terminal, a pair of resistive discs having a radius of curvature conforming to that of the inner surface of said inner cylinder mounted within said inner cylinder whereby electrical contact is made between the circurnference of each said disc and the inner surface of said inner cylinder, said input terminal of said inductive element being connected to one of said pair of discs at a point interior to said circumference, and the output terminal of said inductive element being connected to the other of said pair of discs at a point interior to said circumference, means for applying an input signal between said input terminal of said inductive element and said outer cylinder, and means for deriving an output signal between said outer cylinder and said output terminal of said inductive element.

4. An attenuation equalizer comprising an inner and an outer hollow cylinder of conductive material, a hollow cylindrical sleeve of dielectric material for supporting said inner cylinder coaxially Within said outer cylinder, said sleeve separating the inner surface of said outer cylinder from the outer surface of said inner cylinder, an inductive element having an input and an output terminal, a pair of resistive discs having a radius of curvature conforming to that of the inner surface of said inner cylinder mounted within said inner cylinder whereby electrical contact is made between the circumference of each said disc and the inner surface of said inner cylinder, one of said pair of discs making contact with said inner cylinder adjacent one 'end thereof and the other of said pair of discs making contact with said inner cylinder adjacent 'the other end thereof, said input terminal of said inductive element being connected to substantially the center of one of said pair of discs, and said output terminal of said inductive element being connected to substantially the center of the other of said pair of discs, means for applying an input signal between said input terminal of said inductive element and said outer cylinder, and means for deriving an output signal between said outer cylinder and said output terminal of said inductive element.

5. An attenuation equalizer comprising an inner and an outer hollow cylinder of conductive material, said outer cylinder being longer than said inner cylinder, a hollow cylindrical sleeve of dielectric material having a length substantially the same as that of said inner cylinder, said inner cylinder being coaxially supported within v said outer cylinder and substantially at the longitudinal center of said outer cylinder by said dielectric sleeve, a pair of resistive discs having a radius of curvature conforming to that of the inner surface of said inner cylinder mounted within said inner cylinder whereby electrical contact is made between the circumference of each said disc and the inner surface of said inner cylinder, one of said pair of discs being positioned adjacent one end of said inner cylinder and the other of said pair of discs being positioned adjacent the other end of said inner cylinder, an inductive element having an input terminal and an output terminal, said input terminal of said inductive element being connected to substantially the. center of one of said pair of discs, and said output terminal of said inductive element being connected to substantially the center of the other of said pair of discs, means including impedance matching means for applying an input signal between said input terminal of said inductive element and said outer cylinder, and means including impedance matching means for deriving an output signal between said outer cylinder and said output terminal of said inductive means.

Trevor Apr. 29, 1941 Goldsmith Apr. 2, 1957 

1. AN ATTENUATION EQUALIZER OF THE COAXIAL TYPE HAVING A PAIR OF INPUT TERMINALS AND A PAIR OF OUTPUT TERMINALS AND ADAPTED FOR OPERATION AT VERY HIGH FREQUENCIES, SAID EQUALIZER COMPRISING AN INNER AND AN OUTER HOLLOW CYLINDER OF CONDUCTIVE MATERIAL MOUNTED IN COAXIAL RELATIONSHIP, THE OUTER SURFACE OF SAID INNER CYLINDER BEING SEPARATED FROM THE INNER SURFACE OF SAID OUTER CYLINDER BY A DIELECTRIC MEDIUM, AN INDUCTIVE ELEMENT HAVING AN INPUT AND AN OUTPUT TERMINAL, FIRST AND SECOND RESISTIVE MEANS, SAID FIRST RESISTIVE MEANS SUPPORTING ONE END OF SAID INDUCTIVE ELEMENT WITHIN SAID INNER CYLINDER AND INTERCONNECTING SAID INPUT TERMINAL OF SAID INDUCTIVE ELEMENT AND THE INNER SURFACE OF SAID INNER CYLINDER, AND SAID SECOND RESISTIVE MEANS SUPPORTING THE OTHER END OF SAID INDUCTIVE ELEMENT WITHIN SAID INNER CYLINDER AND INTERCONNECTING SAID OUTPUT TERMINAL OF SAID INDUCTIVE ELEMENT AND THE INNER SURFACE OF SAID INNER CYLINDER, SAID OUTER CYLINDER AND SAID INPUT TERMINAL OF SAID INDUCTIVE ELEMENT COMPRISING SAID PAIR OF INPUT TERMINALS, AND SAID OUTER CYLINDER AND SAID OUTPUT TERMINAL OF SAID INDUCTIVE ELEMENT COMPRISING SAID PAIR OF OUTPUT TERMINALS. 